1. Technical Field
The present disclosure relates to active matrix devices, and more particularly to a liquid crystal display (LCD) device with dummy data lines supplied with gray scale voltages.
2. Description of Related Art
Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products. Resolution of an LCD device is indicated by a number combination, such as 480×272 for a 4.3-inch LCD device, expressed in terms of the number of pixels on the horizontal axis and the number on the vertical axis. Furthermore, as each pixel is composed of R, G, and B sub-pixels, and each sub pixel is electrically connected to a data line, a total of 272 scanning lines extend along the horizontal axis and 480×3 data lines extend along the vertical axis for the 4.3-inch LCD device. In order to reduce costs and the number of driving ICs, half-data line design has been developed.
Referring to FIG. 7, a partial circuit diagram of a typical active matrix display device is shown. The active matrix display device 1 includes a scanning driving circuit 11, a data driving circuit 12, and a display panel 13. The display panel 13 includes a plurality of parallel scan lines Ga1 . . . Gam (m≧1, where m is an integer) connected to the scanning driving circuit 11, a plurality of parallel data lines Dr1 . . . Drn (n≧1, where n is an integer) perpendicular to the plurality of scan lines and connected to the data driving circuit 12, a plurality of pixel electrodes Eij (i,j≧1, where i and j are integers), and a plurality of thin film transistors (TFTs) 14 functioning as switch elements for driving the pixel electrodes Eij.
Two scanning lines Ga(2p+1), Ga(2p+2) (m≧p≧0, where p is an integer) and two data lines Drq, Dr(q+1) (n≧q≧1, where q is an integer) cooperatively define two display pixels. The two scanning lines Ga(2p+1), Ga(2p+2) and n columns of data lines Dr1 . . . Drn drive j pixel electrodes in one row. One data line Drn is connected to two display pixels adjacent to each other along the horizontal axis, and each two adjacent display pixels are driven respectively by the two scanning lines Ga(2p+1), Ga(2p+2), that is, source electrodes 141 of the two adjacent TFTs 14 are connected to one data line Drn, and gate electrodes 140 of the two adjacent TFTs 14 are separately connected to the two adjacent scanning lines Ga(2p+1), Ga(2p+2). For example, when p=0, q=1, the gate electrode 140 of TFT 14 will be connected to the scanning line Ga1, a source electrode 141 is connected to the data line Dr1, and a drain electrode 142 is connected to the pixel electrode E11. Pixel electrode E12 is connected to the same data line Dr1, while the gate electrode 140 of the adjacent TFT 14 is connected to the scanning line Ga2. That is, the data line Dr1 supplies the two pixel electrodes E11, E12 with gray voltages, as shown in FIG. 7.
Referring also to FIG. 8, an enlarged view of part of the active matrix display device 1 of FIG. 7 is shown. A distance and a coupling capacitance (not shown) between the data line Dr1 and the pixel electrode E12 are separately represented as d1 and Csp1. A distance and a coupling capacitance (not shown) between data line Dr2 and the pixel electrode E13 are separately represented as d2 and Csp2. A distance and a coupling capacitance (not shown) between the pixel electrode E12 and the pixel electrode E13 are separately represented as d3 and Csp3.
During operation, when scanning signals are applied to the plurality of scanning lines Ga1 . . . Gam in sequence, the data lines Dr1 . . . Drn provide gray scale voltages for the pixel electrodes simultaneously. When p=0, for example, if the scanning signal is applied to the scanning line Gal, the TFT 14 connected to the scanning line Ga1 is turned on. Consequently, the odd pixel electrodes E11, E13, E15 . . . are written into gray scale voltages to display corresponding gray scales. When the scanning signal is applied to the scanning line Ga2, the TFT 14 connected to the scanning line Ga2 is turned on. Consequently, the even pixel electrodes E12, E14, E16 . . . are written into gray scale voltages to display corresponding gray scales. The pixel electrodes E2j display gray scale in the same driving method: in the first period, the odd pixel electrodes E21, E23, E25 . . . are written into gray scale voltages to display corresponding gray scale, in the following period, the even pixel electrodes E22, E24, E26 . . . are written into gray scale voltages to display corresponding gray scales. The above-mentioned driving method is repeated in the next frame.
During manufacture of such an active matrix display device, exposure shift or uneven etching maybe occur due to limited precision of the manufacturing device. As a result, the differences among the distances d1, d2 and d3 increase. While capacitance is inversely related to the distance, half-data line design increases differences among the capacitances Csp1, Csp2 and Csp3. Consequently, the voltage difference between the adjacent pixels Eij and common electrode (not shown) also increases. Thus, flickering may occur, affecting display quality.
What is needed, therefore, is an active matrix display device to overcome the described limitations.